1. Technical Field
The present invention relates to a tubular burner including: a mixing tube having at a rear end thereof an inlet port into which a fuel gas and primary air flow; and a flame hole member having a plurality of flame holes and being fitted into a front end portion of the mixing tube so that a mixture of a fuel gas and primary air (hereinafter also referred to as “air-fuel mixture”) is ejected from the flame holes for combustion.
2. Background Art
As this kind of tubular burner, there is known one in which are formed, as flame holes, a central main flame hole and a plurality of subsidiary flame holes which are smaller than the central flame hole and are positioned therearound (see, for example, US-A1-5186620, US-A1-20070082309, JP-2012-37109 A, JP-2012-37110 A, and JP-2012-42083 A). The reason for forming the subsidiary flame holes is to stabilize the combustion.
Conventionally, the subsidiary flame holes are evenly disposed over the entire circumference of the central main flame hole. Therefore, the secondary air to be supplied from outside the flame hole member is consumed for the combustion of the air-fuel mixture to be ejected from the subsidiary flame holes. As a result, the secondary air ceases to be sufficiently supplied to the root portion of the main flame that is formed by the combustion of the air-fuel mixture to be ejected out of the central main flame hole. The main flame will then be largely elongated forward to catch the secondary air, and the combustion apparatus provided with the tubular burner will become larger in size.